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Cytology and Cell Biology

Cytology	Cell Biology (Modern Cytology)
Cytology includes the study of Cell organelles (living part of cell) and Cell inclusions (Non-living part of cell) only.	Cell Biology (Modern Cytology) includes study of Cell organelles Cell inclusions along with Physiology of cell Chemistry of cell and Genetic of cells
Cytology deals form and structure of cell.	Cell biology deals with Structure and Function of cell.
Robert Hooke is the father of Cytology.	Swanson is the father of Cell biology or Modern Cytology.

Check check
History
1. Robert Hooke:
  1. Term "Cell" was coined by him in 1665.
  2. Discovered cell form outer bark of Quercus suber. (Cork Oak)
    $Cork oak - Simple English Wikipedia, the free encyclopedia$
  3. Actually it was Cell wall, Dead cell, Attached cell.
  4. Robert Hooke published his finding in a book 📙, Micrographia.
2. A.V. Leeuwenhoek:
  1. Father of Microscopy
  2. Discovered living cell and is free cells.
Cell Theory
1. Cell theory was proposed by Schwann (German Zoologist) and Schleiden (German Botanist).
  1. Note: 1st idea 💡 of cell theory was given by Dutrochet by boiling the leaf of Mimosa pudica in nitric acid and separated the cell.
2. It states that all living being consists of cell and is the smallest structural and functional unit of life.
3. Cell theory was extended by Rudolf Virchow.
  1. Rudolf Virchow proposed "Law of cell lineage" stated "omnis cellula e cellula" meaning all cells are originated from pre-existing cells only by reproduction.
  2. Cell principle/ Cell doctrine/ Modern or modified cell theory = Cell theory + Cell lineage.
4. Exceptions of cell theory
  1. Virus = Obligate parasites, Sub-cellular in nature (Major exception)
  2. Vaucheria (Algae) = Multinucleated
  3. Rhizopus, Mucor (Fungi) = Multinucleated
    1. Rhizopus
      
      Mucor
  4. Paramecium (Protista) = Binucleate/ multinucleated
  5. Opalina (Protist) = Multi-nucleated
Cell size
1. The normal cell size is 0.2 μm to 20 μm.
2. The unit of measurement in micron (μm) in light microscope and is angstron (Å) in electron microscope.
3. Factors affecting cell size are:
  1. [Equation]
    $C e l l s i z e \propto C h r o m o s o m e n u m b e r$ $C e l l s i z e \propto C h r o m o s o m e n u m b e r$
  2. [Equation]
    $C e l l s i z e \propto S i z e o f C h r o m o s o m e$ $C e l l s i z e \propto S i z e o f C h r o m o s o m e$
  3. [Equation]
    $C e l l s i z e \propto 1 M e t a b o l i c a c t i v i t y (∵ S m a l l e r c e l l s a r e m e t a b o l i c a l l y a c t i v e)$ $C e l l s i z e \propto \frac{1}{M e t a b o l i c a c t i v i t y} (∵ S m a l l e r c e l l s a r e m e t a b o l i c a l l y a c t i v e)$
  4. [Equation]
    $C e l l s i z e \propto 1 N u c l e o c y t o p l a s m i c r a t i o (∵ N u c l e o c y t o p l a s m i c r a t i o \propto M e t a b o l i c a c t i v i t y)$ $C e l l s i z e \propto \frac{1}{N u c l e o c y t o p l a s m i c r a t i o} (∵ N u c l e o c y t o p l a s m i c r a t i o \propto M e t a b o l i c a c t i v i t y)$
  5. [Equation]
    $C e l l s i z e \propto 1 S u r f a c e a r e a o f t h e c e l l p e r u n i t v o l u m e (∵ S m a l l e r c e l l s h a v e g r e a t e r s u r f a c e a r e a p e r u n i t v o l u m e)$ $C e l l s i z e \propto \frac{1}{S u r f a c e a r e a o f t h e c e l l p e r u n i t v o l u m e} (∵ S m a l l e r c e l l s h a v e g r e a t e r s u r f a c e a r e a p e r u n i t v o l u m e)$
4. Smallest cell
  1. Smallest cell = Mycoplasma gallisepticum / PPLO(Pleuro pneumonia like organism)/ Joker of Plant Kingdom
    1. Without cell wall
    2. Plant 🌱 diseases caused by Mycoplasma
      1. Bunchy top of Papaya
      2. Little leaf of Brinjal
      3. Clover🍀 dwarf
      4. Mulberry dwarf
  2. Smallest cell with cell wall = Bacteria (Dialister pneumosintes)
  3. Smallest animal cell = Human sperm cell
5. Largest and Longest cell
  1. Largest prokaryotic cell: Spirillum volutant
  2. Animal cell
    1. Largest cell = Ostrich egg cell
    2. Longest cell = Nerve cell
  3. Plant cell
    1. Largest cell = Acetabularia
      1. Unicellular
        Uninucleate
        Belongs to green algae
        Umbrella ☔ shaped algae
    2. Longest cell = Fibre of Ramie (Boehmeria nivea)
Cell Dividing capacity
1. Cellular totipotency (Latin: Totus = all; potens = power)
  1. Capacity of individual or single, nucleated, living vegetative plant cell to regenerate whole plant.
  2. Idea of cellular totipotency was firstly given by Haberlandt.
  3. Phenomenon of cellular totipotency was proved experimentally by Steward and his co-worker.
    1. $Steward experiment |tissue culture | techniques used in cell biology | 2\2 #biology - YouTube$
    2. He used phloem tissue from roots of carrot as an explant.
    3. Used coconut milk in his experiment as liquid media.
      1. Coconut 🥥 milk naturally contain cytokinin which induce cell division.
        So, cytokinin(zeatin) is also called coconut milk factor.
        Zeatin/ Cytokinin/ Kinetin is also rich in immature maize grain.
2. Pluripotency:
  1. Pluripotency is the potential ability of an animal cell to develop into any type of the cell in the animal body but not into whole animal.
  2. Stem cells are only totipotent in animal.
3. Cell Ghosts:
  1. Erythrocyte empties; named so because they are difficult to observe under light microscope due to absence of contents.
  2. Erythrocyte contents come out when a drop of blood is placed in water.
  3. It causes rupturing of erythrocytes or haemolysis.

Cell types on the basis of Nucleus.

Akaryotic cell
1. A denucleated cell
2. E.g.
  1. Mature mammalian RBC
  2. Sieve tube cell
Prokaryotic cell
Mesokaryotic cell
1. Nucleus with Nuclear membrane but lacks histone protein in DNA and nucleolus in nucleus.
2. Cell division occurs by dinomitosis.
3. Rest of characters are same to eukaryotic cell.
4. E.g: Dinoflagelltes
Eukaryotic

S.N.	Prokaryotic cell	Eukaryotic cell
Cell wall	Cell wall when present is non-cellulosic and made up of peptidoglycan (murein) and lipids.	Cell wall present is of Cellulose or Chitin.
Cell membrane	Site of aerobic respiration is mesosome (Cell membrane) because mitochondria is absent.	Site of aerobic respiration is Mitochondria.
Membrane of cell organelles	Membrane bound cell-organelles are absent. So, called single envelop system.	Membrane bound cell organelles are present. So called double envelop system.
Envelope system	Has 1-envelope system.	2-envelop system.
Nucleus	False Nucleus/ Incipient nucleus/ Prokaryon/ Prochromosome/ Diffused fibrillar nucleus/ Genophore/ Nucleoid Nuclear membrane, Nucleoplasm and Nucleolus absent	True nucleus/ well organized Nucleus with nuclear membrane, nucleoplasm and nucleolus.
DNA	DNA Lies in Cytoplasm Double stranded Circular Non-repetitive Without histone proteins Folded with the help of RNA and polyamines.	DNA Lies in Nucleoplasm Double stranded Linear Repetitive Presence of Histone protein Folded with the help of Histone protein
Histone protein	Histone protein absent in DNA. But has polyamine as basic protein which neutralize the anionic charge of inter nucleotide phosphate of DNA.	Histone protein is present in DNA. It neutralizes the anionic charge of inter nucleotide phosphate of DNA. Histone protein is positively(+) charged
DNA:RNA ratio	DNA:RNA ratio = 1:2	DNA:RNA = 1:1
[Equation]﷐𝐴+𝑇﷮𝐺+𝐶﷯ $A + T G + C$ $\frac{A + T}{G + C}$	[Equation] $A + T G + C = 0.88 (i . e ., G + C i s h i g h e r)$ $\frac{A + T}{G + C} = 0.88 (i . e ., G + C i s h i g h e r)$	[Equation] $A + T G + C = 1.52 (i . e ., G + C i s l e s s)$ $\frac{A + T}{G + C} = 1.52 (i . e ., G + C i s l e s s)$
Ribosomes	Ribosomes: 70 s type	Ribosome: Both 70s and 80s (80s main type)
Microtubules and spindle fibres	Microtubules and spindle fibres absent	Microtubules and spindle fibres present.
Cilia and flagella	Cilia and flagella if present are single stranded and made up of flagellin protein.	Cilli/ flagella when present are 11 stranded and shows 2+9 arrangement and made up of tubulin protein.
Cell division	Cyclosis, mitosis, meiosis absent and Amitosis is common.	Cyclosis, Mitosis, Meiosis present and Amitosis rarely found in yeast.
Examples	Monera Bacteria Cynobacteria/ BGA Arachaebacteria Mycoplasma Chlamydia Rickettsia	Fungi Protist Euglena Plants and Animals
Special	Most extensively studied prokaryote is E. coli. Chlamydia and Rickettsia have both RNA and DNA as nucleic acid and are connecting link between virus and bacteria.	Eukaryotic cell differ from prokaryotic cell in having presence of cistrons.

Difference between Plant 🌿 cell and Animal cell

S.N.	Plant cell	Animal cell

	Have cell wall (Main differentiation) Plastids Large central vacuole
	Chromosome with centriole and and lysosome absent.
	Mitosis/ meiosis is Anastral type.	It is Astral or Amphiastral type.
	Inorganic crystals are common in cytoplasm.
	Sphaerosome, Glyoxisome, Lomasome are present.
	Cytokinesis by cell plate.	Cytokinesis is but furrowing.
	Reserve food is Starch.	Reserve food is Glycogen.
	Plant cell don't burst in hypotonic solution due to presence of cell wall.	RBC gets burst because it has no cell wall.
	All nucleated cells are totipotent.	Fertilized egg and Stem cells in blastocyst are totipotent.

Cell Organization

Cell wall

Common in plants; also in bacteria, cyanobacteria.
It is non-living.
Constituents
1. Plant cell wall is made up of
  1. Cellulose
    1. β-D glucose
  2. Hemicellulose and
    1. Arabinose
    2. Mannose
    3. Xylose
    4. Galactose, etc
  3. Pectin
    1. Galactose
    2. Galacturonic acid and
    3. Arabinose
2. In bacteria and cyanobacteria, cell wall is made up of
  1. Murin/
  2. Mucopeptide/
  3. Peptidoglycan
    1. Polysaccharide part of peptidoglycan is the polymer of N-acetyl glucosamine(NAG) and N-acetyl muramic acid(NAM).
3. In fungi, cell wall made up of Chitin/ fungal cellulose.
  1. Chitin [Equation]
    $(C 22 H 54 N 4 O 21) n$ ${(C_{22} H_{54} N_{4} O_{21})}_{n}$ is polymer of N-acetyl glucosamine(NAG).
    1. NAG is amino acid.
Cell wall is
1. Porous
2. Permeable
3. Inert
4. Hydrophilic
5. Semitransparent
6. Protective covering secreted by Cytoplasm.
Plant cell without cell wall is
1. Mycoplasma,
2. Gametes,
3. Zoospores,
4. Slime moulds (Myxomycetes).
Cell wall formed during cytokinesis from vesicles of ER and Golgi bodies.

Layers of Cell wall

In higher plants, cell walls consists of different layers

Middle lamellae:

Outermost layer of cell wall.
Layer between cell wall of two cell is Middle lamellae.
It is cementing layer that joins 2 adjacent plant cells together.
1. It contains cementing material Ca-pectate and Mg-pectate. (Mainly Ca-pectate)
2. Retting of fibres and ripened fruit becomes soft due to dissolution of middle lamellae (dissolution of Ca-pectate) and dissolution is brought by Pectinase enzyme.
  1. Retting of fibres

First layer to be formed during cytokinesis by vesicles of Golgi bodies and ER.

During cytokinesis, vesicles of golgi bodies and spindle protein come to the equator called Phragmoplast.
Phragmoplast(Precursor molecule) form Cell plate.
Cell wall is formed from cell plate.

[Equation]

V e s i c l e s o f G B + S p i n d l e p r o t e i n \to P h r a g m o p l a s t \to C e l l p l a t e \to C e l l w a l l

$V e s i c l e s o f G B + S p i n d l e p r o t e i n \to P h r a g m o p l a s t \to C e l l p l a t e \to C e l l w a l l$

Middle lamellae is totally absent in all unicellular plant and all fungi.
Grows by
1. Intussusceptions or
  1. Primary wall stretched and materials of secondary wall are deposited
2. Apposition
  1. Materials of secondary wall are deposited in the form of thin layer.

Primary cell wall:
1. Elastic in nature
2. Unipartite (Single layer)
3. It is found universally in all cells having cell wall.
4. Lies inner to middle lamella.
5. Made up of
  1. Cellulose (β-D glucose unit),
  2. Hemicellulose and
  3. Pectin roughly in equal amount.
    Note: Starch is formed by α-D glucose unit.
6. Lignin is never found in primary cell wall but may have Silica, Wax, Cutin, etc.
7. Primary cell wall is common in Parenchyma and Meristematic cells.
8. Grows by Intussusception.
Secondary cell wall:
1. Thick
2. Inelastic in nature
3. Present inner to primary cell wall.
4. Tripartite namely
  1. S1
  2. S2 and
    1. S2 is thickest layer.
  3. S3
5. Developed by Apposition.
6. Pits is common.
7. Provides mechanical strength, stiffness and hardness to cell.
8. Made up of Cellulose (high), sometimes hemicellulose and additionally by:
  1. Cutin (Waxy substance)
    1. Found in epidermis and its continuous layer is called Cuticle.
      1. Cuticle is thick layered by Xerophytes.
      2. Cuticle is thin layered in mesophytes.
      3. Cuticle is absent in hydrophytes.
  2. Suberin:
    1. In Cork cells and Endodermis.
    2. It makes the cell impermeable.
    3. It checks evaporation of water.
    4. It is mixture of fatty acids.
  3. Pectin
    1. In Collenchyma
    2. Provides elasticity
  4. Lignin
    1. In xylem vessels, Sclerenchyma, Tracheids (Dead cells)
    2. Lignin is permeable to water and lignified cells are thick-walled and dead.
    3. Gives highest rigidity.
  5. Wax: On floating leaves
  6. Silica:
    1. Deposited on the cell wall and gives rough touch.
    2. E.g.: Equisetum (Horsetail)
  7. Mucilage
    1. Chemically, it is complex carbohydrate.
    2. Slimy substance, slippery to touch.
    3. Due to this, the cells can withstand extreme temperature.
    4. E.g.:
      1. Aloe vera
      2. Hibiscus 🌺 (China rose)
Tertiary cell wall
1. Sometimes S3 of secondary wall is called as tertiary wall when it contains Xylon(Polymer of D-xylose) and Mannon.
2. Thick and warty in appearance.
3. E.g.: Tracheids of gymnosperm

Cell to cell conduction system

S.N.

Symplasm (Living sytem)/ Plasmodesmta

Apoplasm (Non-living system)/ Pits

Plasmodesmata are living cytoplasmic strands which establish connections between adjacent plant cells.

Unthickened area in cell wall where secondary wall is not produced is called as pit.

Through the plasmodesmata, all the protoplasts of a living system are linked to form a continuous system called symplasm.

Dead cells are interconnected by means of pits and form Apoplasm.

Molecular Expressions Cell Biology: Plant Cell Structure - Plasmodesmata

Plasmodesmata is modification of cell membrane and found only in multicellular plant.

Difference between Primary Cell Wall and Secondary Cell Wall

Pits are found only in secondary wall.
Pit consists of Cavity and Pit membrane.
- Pit membrane is middle lamella + primary cell wall (but mainly primary cell wall)

Types of pits

Simple pits	Bordered pits (Cavity flask shaped)
Are uniform in diameter. Found in Angiosperms. It lacks pit chamber and torus. E.g.: Companion cells and Sieve tubes.	Cavity flask shaped. Found in Gymnosperms. It contains pit chamber and torus. Torus is swollen portion of pit membrane and acts as valve. E.g.: Vessels and Tracheids.

Note:

Sclerenchyma fibre has simple pits as well as bordered pit.
Aspirated pit is a non-functional pit in which pit aperture is blocked permanently by torus.

Cell constituents
1. Cellulose is most abundant carbohydrate of Biosphere.
  1. Cotton contains highest amount of Cellulose(90%) in biosphere.
2. Chitin is the second most abundant carbohydrate.
3. [Equation]
  $β - D G l u c o s e - \to - - 600 C e l l u l o s e - \to - - 100 M i c e l l e - \to - 20 M i c r o f i b r i l - \to - 250 M a c r o f i b r i l$ $𝛽 - D G l u c o s e \overset{600}{\to} C e l l u l o s e \overset{100}{\to} M i c e l l e \overset{20}{\to} M i c r o f i b r i l \overset{250}{\to} M a c r o f i b r i l$
4. Structural unit of Cell wall are
  1. Micelle
  2. Microfibril
  3. Macrofibril

Cell coat/ Glycocalyx
1. In animal cell, cell wall is absent and outermost covering is called Cell coat 🧥 or Glycocalyx.
2. Cell coat is made up of Oligosaccharides and terminal sugar of oligosaccharide is Sialic acid.
  1. The layer of carbohydrate is oligosaccharide in animal cell helps in cell to cell recognition.
3. [Equation]
  $G l y c o c a l y x = G l y c o p r o t e i n + G l y c o l i p i d .$ $G l y c o c a l y x = G l y c o p r o t e i n + G l y c o l i p i d .$
  1. Glycoprotein and Glycolipid help in Site recognition.
  2. So, Glycocalyx is site of Cell recognition.
  3. Glycocalyx makes the cell membrane asymmetric.
4. Note: In cell Recognition: Oligosaccharide > (Glycoprotein + Glyolipid)

Protoplast

Plasma membrane/ Cell membrane/ Plasmalemma

Cell membrane is
1. Thin,
2. Elastic,
3. Living,
4. Selectively or Differentially permeable membrane.

Made up of phospholipid (common) and protein.

Head = Hydrophilic
Tail = Hydrophobic

Forms of Lipid in Cell membrane	Forms of Protein in Cell membrane	Forms of Carbohydrate in cell membrane
Fluidity and Elasticity of cell membrane depends upon lipid. Phospholipid Frame work molecule of cell membrane Phospholipid is amphipathic molecule, because it shows double property, hydrophilic as well as hydrophobic. Phospholipid membrane is always bilayered. Glycolipid Cholesterol	In general, Protein > Lipid in cell membrane but in Myelin sheath Lipid(75%) > Protein (25%). Extrinsic or Peripheral protein (25%) = Can easily be exuded out Intrisic or Integral protein (75%)	Glycolipid Glycoprotein
	Arginine and Lysine are amino acids found in cytoplasmic membrane.

Thickness of Plasma membrane is 75 Å[Equation] .
[Equation]
$P l a s m a m e m b r a n e + O r g a n e l l e m e m b r a n e = B i o l o g i c a l m e m b r a n e$ $P l a s m a m e m b r a n e + O r g a n e l l e m e m b r a n e = 𝑩 𝒊 𝒐 𝒍 𝒐 𝒈 𝒊 𝒄 𝒂 𝒍 𝒎 𝒆 𝒎 𝒃 𝒓 𝒂 𝒏 𝒆$

Different Models of Cell membrane

Trilamellar model or Sandwich model	Unit membrane model	Fluid Mosaic Model

Proposed by Danielli and Davson. Accordingly, plasma membrane consists of 3 layers. Outer: Protein Middle: Bilayered phospholipid Inner: Protein Protein is Globular type. Sequence of Lipid and Protein is [Equation]𝑷−𝑳−𝑳−𝑷. $P - L - L - P .$ $𝑷 - 𝑳 - 𝑳 - 𝑷 .$	Proposed by Robertson. Unit membrane model is similar to Trilamellar model except nature of Protein i.e., Fibrillar type. Sequence of lipid and Protein is [Equation]𝑷−𝑳−𝑳−𝑷. $P - L - L - P .$ $𝑷 - 𝑳 - 𝑳 - 𝑷 .$	Proposed by Singer and Nicolson. Latest and most widely accepted model. This model is based on freeze etching/ fracture technique. This model differs from trilamellar model and unit membrane model in the arrangement of protein. [Equation] $P - L - P - L O R L - P - L - P .$ $𝑷 - 𝑳 - 𝑷 - 𝑳 O R 𝑳 - 𝑷 - 𝑳 - 𝑷 .$ "Protein iceberg in sea of lipid" meaning lipid form continuous layer and protein molecules are randomly arranged. Proteins are Extrinsic (surface, 25%) Tunnel (In between extrinsic and intrinsic) Intrinsic (Inner, 75%) All carrier proteins are intrinsic protein. Lipid and proteins in the membrane are held together due to hydrophobic attraction. The rotational movement of lipid molecule is called Flip-flop mechanism.

Functions of Plasma membrane:
1. Plasma membrane controls passage of material in and out of cell with the help of Ca2+ and CAMP(Cyclic Adenosine Monophosphate).
2. Exchange of gases like CO2 and O2 is possible through membrane.
3. Plasma membrane also show bulk transport.
  2. Active transport requires energy as well as carrier protein.
  3. Passive transport requires neither energy nor carrier protein.
    Exception: Faciliated diffusion is a passive transport which doesn't require energy but requires carrier protein.

Junction complex

Junction complex is found only in multicellular organism for cell adhesion.
It is of following types.

Plasmodesmata	Desmosome	Tight junction	Gap junction	Interdigitation	Terminal bar
Plasmodesmata are living cytoplasmic strands which establish connections between adjacent plant cells. Plasmodesmata is modification of cell membrane and found only in multicellular plant.	acts like a spot weld between two adjacent animal cells.	watertight seal between two adjacent animal cells	channels between adjacent animal cells	Interwoven processes	unresolved group of junctional complexes that attach adjacent epithelial cells on their lateral surfaces

Modification of cell membrane:

A) Mesosome	B) Lomasome	C) Lamellosome	D) Microvilli

Infoldings of cell membrane in bacteria (Gram +ve) Helps in respiration and Cell division.	Lomasome is present in between cell membrane and cell wall and thus called as extracellular cell organelle. It is found only in fungus. It helps in proliferation and elongation of cell wall for diffusion.	Infolding of cell membrane in Blue Green Algae. Helps in expansion of cell wall.	Finger like evagination (outfolds) in cells of digestive tract for ultra-absorption of liquids.

Protoplasm

About protoplasm
1. Purkinje coined the term Protoplasm.
2. Huxley defined it as "Physical basis of life" because all the processes of life occur in protoplasm.
3. Best material to study protoplasm is Slime moulds (Because of absence of Cell wall).
4. Protoplasm is the highly organised and most active chemical system of nature with maximum energy conversion.
5. Living beings differ from non-living in having protoplasm.
6. Protoplasm constituent
  1. Highest % of water is present in protoplasm (75-85%).
    1. The major inorganic constituent of protoplasm is water.
  2. Constituent elements of protoplasm by weight:
    1. Oxygen = 62% (HIGH)
    2. Carbon = 20%
    3. Hydrogen = 10%
    4. Nitrogen = 3% (LOW)
  3. The ratio of inorganic to organic substance in cell is 1:9.
7. Protoplasm exists in two different forms
  [Equation]
  $(S o l (i n n e r) ⟷ G e l (o u t e r)) (L i q u i d l i k e) (J e l l y l i k e)$ $\underset{(L i q u i d l i k e) (J e l l y l i k e)}{(S o l (i n n e r) ⟷ G e l (o u t e r))}$
  1. Sol-gel interconversions is because of colloidal nature of protoplasm.
  2. Outer gel like called ectoplast (plasma gel) and inner sol part called endoplast (plasma sol).
  3. The conversion of plasmasol into plasmagel is a physio-chemical phenomenon.
  4. Cyclosis occurs in endoplast region.
    2 types:
    1. Rotation: Movement in one direction (Clockwise/ anticlockwise) around vacuole inside a cell
      1. Ex: Hydrilla, Vallisnaria.
    2. Circulation: Movement is in different direction around vacuole inside the cell
      1. E.x: Tradescantia
  5. Brownian movement, Tyndal effect, Cyclosis and Amoeboid movement in cells are due to colloidal nature of protoplasm.
  6. Protoplasm coagulates at above 60o or when treated with concentrated acids/bases.
    Notes: Enzymes denatured at high temperature and inactivated at very low temperature. So, optimum temperature is required for the functioning of enzyme.
  7. Deutoplasm is the non-living substance formed by the protoplasm during metabolism. E.g., liquid droplets, yolk, etc.

Cytoplasm

Cell organelles

Organenelle bounded by Triple membrane
1. Transosomes
  1. Transosome is found in ovarian follicle of bird.
  2. It takes part in synthesis of yolk (vitellogenesis).
    Note: In other anima, Vitellogenesis takes place with the help of Golgi bodies(manily) + ER + microfilaments.

Organelle bounded by Double membrane

Plastid
1. Discovered and term given by Haeckel.
2. Mainly found in plants and certain protist, absent in fungi.
3. Involved in formation and storage of carbohydrate.
4. Usually 3 types, on the basis of Pigments.
5. Leucoplast:
  1. Largest plastid.
  2. Usually found in underground parts.
  3. Function: Storage of reserve food material.
    1. 3 types on the basis of nature of food stored:
    2. Amyloplast = Stores Starch = E.g.: Potato, Rice, Wheat
    3. Proteinoplast/ Aleuronoplast = Stores Protein = E.g.: Maize
    4. Elaioplast/ Oleosome/ Lipoplast = Stores oil/fat = E.g.: Ricinus (Castor seed)(Dicot with Endosperm)
6. Chromoplast:
  1. 2nd largest plastid.
  2. Chromoplast is coloured plastid (other than green).
  3. Have fat soluble carotenoids to provide colour to fruits, seeds and flowers.
  4. Formed by
    1. Chloroplast (Due to replacement of chlorophyll pigment by other coloured pigment)
      1. Green tomato changes into Red tomato 🍅 due to replacement of chlorophyll by pigment Lycopin.
      2. Green chilies change to Red chilies due to replacement of chlorophyll by pigment Capsanthin.
    2. Leucoplast (Due to development of coloured pigment)
      1. Carrot
  5. Other coloured plastids are:
    1. Phaeoplast: It is brown plastid. E.g: Brown algae
    2. Rhodoplast: It is red plastid. E.g: Red algae
7. Chloroplast:
  1. Discovered by Sachs but named chloroplasts by Schimper.
  2. Chloroplast is green plastid.
  3. Function: Formation of carbohydrate and Store starch temporarily.
  4. Also called Kitchen of cell, Photosynthetic apparatus, Autoplasts.
  5. Common in all photosynthetic organism except photosynthetic bacteria and cyanobacteria (BGA).
    1. In photosynthetic bacteria and Cyanobacteria pigments are found in Chromatophore (Scattered thylakoids).
  6. Shape of chloroplast:
    1. Shape generally Discoid/ Oval/ Tablet 💊 shaped or Biconvex.
    2. Cup 🥤 shaped = Chlamydomonas
    3. Spherical shaped = Chlorella
    4. Spiral/ Ribbon shape/ Scalariform = Spirogyra
    5. Girdle/ Ring/ Collar/ Horse 🐎 shoe shaped = Ulothrix
    6. Reticulate/ Net like = Oedogonium
    7. Stellate or Star shaped = Zygnema (Double star)
    8. Discoid shaped = Vaucheria, Chara
  7. No. of chloroplast
    1. Single chloroplast = Chlamydomonas and Chlorella
    2. Single chloroplast in each cell = Ulothrix
    3. Double chloroplast in each cell = Zygnema
    4. No. of chloroplast is maximum in mesophyll cells of leaf.
  8. Structure of Chloroplast
    2. Chloroplast is differentiated into Grana and Stroma.
    3. Grana
      1. Grana is the site for Light reaction.
        Note:
        Agranal chloroplast is common in algae and bundle sheath chloroplast of C4 plants.
        Agranal chloroplast in which thylakoids are not stacked is called Lamellar chloroplast.
        Thylakoids
        Thylakoids (baggy trousers) are structural unit of chloroplast, whereas
        Quantasomes
        Quantasomes are functional unit of chloroplast.
        Photosynthetic pigments are present in membranes of thylakoids at specific areas called Quantasomes. (280 pigments)
        Quantasomes of Eukaryotes consists 230 chlorophyll molecules (160 chl-a +70 chl-b) and 50 carotenoids molecules.
        Quantasomes of Prokaryotes consists of only 50 chlorophyll molecules.
        Grana are interconnected by means of Stroma lamellae or Fret membrane or Intergranal thylakoid.
    4. Stroma
      1. Stroma is the ground substance of chloroplast.
      2. Stroma includes:
        Matrix
        Matrix contains enzymes of dark reaction/ CO2 fixation.
        DNA +ribosome
  9. Blue green algae lacks chloroplast, site of photosynthesis is photosynthetic lamellae.

Mitochondria

Power house of Cell or Electric house of Cell or Cellular furnace or ATP mills.
Discovered by Kolliker in striated muscle of insects.
Benda used the term mitochondria.
Altman gave the term "Bioplast" for mitochondria.
Size varies from 0.5 to 1 μm.
Absent in all prokaryotes, anaerobic eukaryotes and present in all aerobic eukaryotes except mature mammalian RBC, cancareous cell, sieve tube of phloem.
Note: RBC at maturity obtains energy of glycolysis.
Structure of Mitochondria

Mitochondria - Definition, Structure, and Function with Diagram

Membranes
1. Outer membrane is permeable due to porins (special protein function as channel for entry and exit of protein) whereas inner membrane in permeable.
  1. Outer mitochondrial chamber contain enzyme adenylate kinase.
2. Inner membrane has infolding called Cristae (in animals) and tubuli or microvilli (in plants).
  1. Cristae is the site of oxidation-reduction.
  2. Inner membrane/ Cristae bear electron transport chain and tennis racket like particles called Oxysomes.
  3. Oxysomes are called Functional unit of Mitochondria.
  4. Oxysome is differentiated into
    1. Head
      1. Also called F1 particle.
      2. Contains enzyme ATPase.
      3. ATPase helps in final step of ATP syntheses.
    2. Stalk
    3. Base
      1. Also called Fo particle.
      2. ETS (Electron transport system) takes place.
      3. It has proton channels.
        When 2 protons pass through proton channel, 1 ATP is released.
        But, according to new concept, it is accepted as 1 ATP is released when 3 electrons are passed through proton channel.
Matrix
1. About 70% of total cell enzymes are found in mitochondria.
2. Enzymes of Kreb's cycle are found in matrix of mitochondria except 'Succinic dehydrogenase' which remains bounded with Inner membrane of mitochondria.
3. Enzyme for fatty acid synthesis, amino acid synthesis, etc. are also found in matrix of mitochondria except "ATPase" and "Cytochrome oxidase". (Located in inner membrane of mitochondria).
4. Matrix of mitochondria is rich in Mn.

The process of ATP synthesis in mitochondria is called Oxidative Phosphorylation which is O2 dependent but light independent.
Mitochondria of a cell are collectively called Chondriome.
Mitochondria whose outer membrane is removed are called Mitoplasts.
Acristate (no cristae) mitochondria is found in spermatid.
Function
1. Petite character in yeast is due to mitochondrial inheritance.
2. Mitochondria helps in elongation of fatty acid.
3. It forms the middle piece of sperm.

Organelle bounded by Single membrane

Endoplasmic reticulum

Protein_translation

1 Nucleus   2 Nuclear pore   3 Rough endoplasmic reticulum (RER)   4 Smooth endoplasmic reticulum (SER)   5 Ribosome on the rough ER   6 Proteins that are transported   7 Transport vesicle   8 Golgi apparatus   9 Cis face of the Golgi apparatus   10 Trans face of the Golgi apparatus   11 Cisternae of the Golgi apparatus

Firstly observed by Porter from liver cells.
ER is also called
1. Working bench of cell
2. Pipeline of cell or
3. Endoskeleton
4. Organelle of Membrane factory
5. Organelle of Detoxification
Extensively developed in Pancreas, Liver, Digestive gland, Fibroblast and poorly developed in sperms, meristematic cells, etc.
Unit membrane structure, bounded by single trilaminar lipoprotein membrane.
Not visible under light microscope.
Absent in
1. All prokaryotic cell
2. Some eukaryotic cells like
  1. Mammal's RBC
  2. Egg
  3. Embryonic cell
  4. Monocyte of WBC
3. Note: ER is poorly developed in rapidly dividing cell. E.g: Meristematic cells
It is made up of
1. Cisternae (Flattened sac/bag)
  Note: Cisternae is not parallel in ER but they are parallel in Golgi bodies.
2. Tubules
3. Vesicles
ER continues from nuclear membrane to cell membrane.
ER continue from one cell to another by plasmodesmata is called Desmotubule.
ER forms more than 50% of total membranes in the eukaryotic cells and occupies 10% of total cell volume.

ER is of 2 types:

Rough Endoplasmic reticulum	Smooth Endoplasmic Reticulum
Forms [Equation]﷐﷐2﷮3﷯﷮𝑟𝑑﷯ $2 3 r d$ ${\frac{2}{3}}^{r d}$ of total ER. 80s ribosomes are attached by their largest subunit with the help of glycoprotein called Ribophorin. Mainly consists of Cisternae and a few tubules. Arises from nuclear membrane. Function: Protein synthesis and Glycosylation.	Forms [Equation]﷐﷐1﷮3﷯﷮𝑟𝑑﷯ $1 3 r d$ ${\frac{1}{3}}^{r d}$ of total ER. Lacks attached ribosomes. Mainly consists of network of tubules and vesicles. Arises from RER. Function: Lipid metabolism.

The broken part of ER (RER) produced during ultracentrifugation is called Microsome.
Part of cytoplasm which is basophilic due to presence of RER of ribosome is known as ergastoplasm.
Nissl's granules is modification of RER/ Ribosome.
1. Nissl's granules are rich in RNA followed by protein.
RER without ribosomes are called Transitional ER.
SER present in epithelial cell of retina eyes is called Myloid bodies (responsible for photoreception).
Annulate lamellae are the precursor of ER.
Special type of ER in skeletal muscle cells are called Sarcoplasmic reticulum (involves in release of Ca++).
Ca++ helps in muscle contraction in fusion of vesicles.
Microbodies called sphaerosome are formed by SER.
RER in association with golgi complex gives rise to Lysosome.
SER in liver cell helps in
1. Detoxification of harmful chemicals
2. Glycogenesis (formation of glycogen from glucose) + Glycogenolysis (Breakdown of glycogen into glucose)
Function of ER
1. It provides mechanical support due to presence of microtubules and thus called as Endoskeleton of cell.
  Note: Structural skeletal structure of cells i.e., cytoskeletal of cells are microtubules, microfilament and intermediate filament.
2. Helps in intercellular and intracellular transport and provide mechanical supports to cytoplasm.
3. Keep cell organelles in position.
4. Formation of nuclear membrane and cell membrane. So, called membrane factory of cell.
5. Formation of
  1. Vacuoles,
  2. Lysosomes,
  3. Glyoxysome,
  4. Golgi bodies,
  5. Exine of pollen grain.
  6. Zymogen (IOM 2009)
6. Detoxification of toxic substance.
  1. Organelle of Detoxification.
7. The major phospholipid synthesized in ER is Lecithin (Phosphatidylcholine).

Golgi bodies
2. Discovered by Camillo Golgi from nerve cell of cat 🙀 and Barn owl.
3. Also called Idiosome/ Dalton complex/ Middle man of cell.
  1. 1st stained GB by using Sudan III. So, also called Baker's bodies.
  2. Dictyosome is the name of golgi body but it is used only in Plant cell.
4. Absent in
  1. All prokaryotic cell
  2. Some Eukaryotic cell
    1. RBCs
    2. Sieve tube
    3. Sperm of Bryophyte and Pteridophyte
    4. Cells of Fungi
5. Formed from Vesicles of SER.
6. Consists of
  1. Cisternae (parallely arranged)
    1. New cisternae are constantly formed by budding off SER and fusion of vesicles. This outside convex known as 'Forming face'.
  2. Tubules and
  3. Vesicles.
7. Microtubules are never found in Golgi body.
8. Golgi apparatus is said to be
  1. "Principal director of macromolecular traffic 🚥 in cell".
  2. Middle man of the cell.
9. Maximum number of golgi bodies are found in Rhizoidal cell of Chara.
10. Golgi complex is involved in the formation of Zymogen granule.
11. Function
  1. Helps in secretion and storage of secretions.
  2. Chemically modify and transport the materials received by it.
  3. Cell plate 🍽 formation during cytokinesis.
    Note: Vesicles of Golgi bodies and Spindle protein form Phragmoplast.
  4. Helps in formation of lysosome.
  5. Formation of Acrosomes in sperms.
    1. Acrosome helps in penetration.
  6. Secretion of Mucilage in root tip region.
    1. Mucilage helps in lubrication.
  7. Formation of special type of carbohydrate called Sialic acid found in cell membrane.
  8. It helps in formation of
    1. Yolk,
    2. Melanin granules,
    3. Hemicelluloe,
    4. Galactose.
  9. It helps in Glycosidation and Glycosylation.
    1. [Equation]
      $L i p i d + C a r b o h y d r a t e - \to - - - - - - G l y c o s i d a t i o n G l y c o l i p i d$ $L i p i d + C a r b o h y d r a t e \overset{G l y c o s i d a t i o n}{\to} G l y c o l i p i d$
    2. [Equation]
      $P r o t e i n + C a r b o h y d r a t e - \to - - - - - - G l y c o s y l a t i o n G l y c o p r o t e i n$ $P r o t e i n + C a r b o h y d r a t e \overset{G l y c o s y l a t i o n}{\to} G l y c o p r o t e i n$
    3. Note:
    4. Glycosidation and Glycosylation are first started in ER.
    5. All complex carbohydrate except Glycogen are synthesized by GB.
    6. Protein packaging.
  10. Special point
    1. Common enzyme of ER and GB
      1. Peptidyl transferase = Main enzyme of RER
      2. Glycosyl transferase = Main enzyme of GB
Vacoles
Microbodies
1. Lysosome
  1. Acid phosphatase is the marker enzyme of Lysosome.
  2. The Lysosome are
    1. Produced by Golgi bodies,
    2. Eats Vacuoles and
    3. Associate with Endoplasmic reticulum for Excretion.
2. Peroxisome
  1. Photorespiration
3. Glyoxysome
4. Sphaerosome
  1. Plant Lysosome.
5. Lomasomes
  1. Fungi

Organelle without membrane
1. Ribosomes
  1. Discovered and named Ribosome by Palade.
    1. So also called Palade particle.
  2. Also called
    1. Engine of the cell
    2. Protein factory 🏭 of the cell
    3. RNP (Ribonucleo protein particle)
  3. Smallest, unmembranous, Electron microscopic and Most abundant cytoplasmic organelle.
    Note: The smallest membrane bounded cell organelle is Lysosome.
  4. Made up of r-RNA and Protein.
    [Equation]
    $↓ ↓$ $↓ ↓$
    [Equation] $S y n t h e s i z e d i n N u c l e o l u s S y n t h e s i z e d i n C y t o p l a s m$ $S y n t h e s i z e d i n 𝑵 𝒖 𝒄 𝒍 𝒆 𝒐 𝒍 𝒖 𝒔 S y n t h e s i z e d i n 𝑪 𝒚 𝒕 𝒐 𝒑 𝒍 𝒂 𝒔 𝒎$
  5. Ribosomes are formed inside Nucleolus.
    Note: Ribosomal factory of cell is Nucleolus.
  6. Measuring unit of Ribosome = Svedberg unit (S)
    S [Equation]→
    $\to$ $\to$ Sedimentation coefficient (Rate of settlement) [i.e., 1 S = 10-13 sec]
  7. Ribosomes are isolated from other cell organelle by Fractionation and Ultra centrifugation.
  8. Ribosome helps in Protein synthesis.
  9. Found in both prokaryotes and eukaryotes except RBC and Sperms.
  10. Types of Ribosomes
    1. 70s ribosomes
      1. Found in Prokaryotic cell and in Mitochondria and Chloroplast of Eukaryotic cell.
      2. Sub-units
        30s (has single r-RNA)
        50s (has two r-RNA)
      3. Note:
        Total r-RNA in 70s ribosome = 3 and Total proteins = 55 proteins.
        55s ribosomes is found in mammals mitochondria not 70s and 55s has sub-units 35s and 25s.
    2. 80s ribosomes:
      1. Found in Eukaryotic cell
        Free = Synthesize non-secretory, non-export protein
        RER = Synthesize secretory export protein
      2. Sub-units
        40s = has single r-RNA
        60s = has 3 r-RNA
      3. Note:
        Total r-RNA in 80s ribosome = (1+3)=4 and total protein = 80 proteins.
        Two ribosomal sub-units are joined by Mg++.
        When Mg++ concentration is increased 10 times 2 ribosome combine to form dimer.
        During protein synthesis no. of ribosomes (6 to 8) are found to attach with m-RNA and polysome/ polyribosome/ Ergasomes.
        During protein synthesis smaller subunits of ribosome attach to m-RNA not the bigger one.
        Ribosomes are also found in organelle of eukaryotic cells like plastids, mitochondria and nucleus. So ribosomes are also called Organelle within organelle.
  11. Which of the following is/are electron microscopic?
    1. DNA
    2. Ribosomes
      1. DNA and RNA are observed by X-ray crystallography.
    3. RNA
    4. All
2. Centrioles
3. Cytoskeleton
  1. Microtubules
  2. Microfilaments
  3. Intermediate filament
4. Nucleolus
5. Chromosomes

Cell Inclusions
1. Reserve food
  1. Carbohydrate
  2. Fats
  3. Proteins
2. Secretory substances
  1. Colouring matter
  2. Enzymes
  3. Nectar
  4. Pigments
3. Excretory substances
  1. Alkaloids
  2. Glucosides
  3. Tannins
  4. Gum
  5. Resins
Cytosol
1. Clear optically homogenous fluid portion of cytoplasm after removal of cell organelles and cell inclusions is known as Cytoplasmic matrix/ Cytosol/ Hyaloplasm or Ground plasm.
2. The ribosome containing ground substance is called Ergastoplasm.

Nucleus

Robert Brown discovered Nucleus from Root cells of Orchid.
Hammerling proved that nucleus is control centre of cell on the basis of his grafting experiment on Acetabularia.
Nucleus is also called Controlling centre of Cell/ Brain 🧠 of Cell/ Director of cell/ Apparatus of heredity.
It is not considered as an organelle.
Largest extracytoplasmic component of cell.
1. Note: The smallest component being Microfilament.
No. of Nucleus/cell as follows:
1. Uninucleated cell = Common
2. Binucleated cell =
  1. Paramecium = Dimorphic nucleus
  2. 2o mycelium of Ascomycetes and Basidiomycetes
3. Multinucleated cell = 2 types
  1. Syncyte: Produced due to fusion of many cells.
    1. Examples
    2. Bone marrow
    3. Striated muscles
    4. Ascaris (Epidermis)
  2. Coenocyte: Formed by repeated nuclear divisions without corresponding cytoplasmic divisions.
    1. Hyphae of Phycomycetes
    2. Xanthophyceae
      1. Vaucheria
      2. Botrydium
    3. Latex cells
4. Anucleated cell: Cell without nucleus
  1. Examples
  2. Plant = Sieve tube at maturity
  3. Animal = Mammal's RBC (Exception: Camel 🐫, Ilama)

Structure of Nucleus

Nuclear envelope/ Karyotheca/ Nuclear envelope:
1. Double layered, lipoproteinaceous.
2. Inner nuclear membrane is smooth as it lacks ribosome.
3. It separates nucleoplasm from cytoplasm.
4. The space between two nuclear membrane is called Perinuclear space (50-70 [Equation]﷐𝐴﷮𝑜﷯
  $A o$ $\overset{o}{A}$ ).
5. Having pores (pore complex) which is Octagonal.
  1. In the pore there is the presence of gates know as Annulus which allow only certain substances to go out through nuclear pore.
Nucleoplasm/ Nuclear sap/ Karyoplasm/ Karyolymph:
1. Includes nucleotides and different ions (Mn++, Mg++).
2. Cyclosis is absent as its viscosity is not constant.
Nucleolus/ Plasmosome:
1. Fontana discovered Nucleolus but term given by Bowman.
2. It is membraneless structure and also called "Ribosomal factory of the cell".
3. Largest part of nucleus.
4. It is colloidal mass and contains
  1. rRNA,
  2. Non-histone acidic proteins but has no DNA.
5. The shape of nucleolus is maintained by Ca++ and Mg++.
6. Biogenesis of nucleolus occurs at 2o constriction-I of SAT chromosome.

Chromatin

Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch. (3) Short arm (p). (4) Long arm (q).

histone-modifying en4me
marked
nucleosome
heterochromatin protein
oooooooooooo
oooooooooooo
heterochromatin
euchromatin

kinetochore
nuclear
erwelope
sister
chromatids
condensing
mitotic
spindle
forming
centrosome
fragments of nuclear envelope
kinetochore microtubule
kinetochore
microtubule
shortening
centrosome
rnoving wtward
prophase
metaphase
early anaphase

Term Chromatin was given by Flemming.
Name Chromosome by Waldeyer.
Made up of DNA (acidic, -ve charged) and histone protein (basic, + charged).
In ultrastructure, chromatin appears like beads on a string.
1. Beaded structure is known as Nucleosome.
2. Each Nucleosome has 8 histone molecule (i.e., 2 copies of 4 types).
  1. 4 types are
  2. H2A,
  3. H2B
  4. H3
  5. H4 and
    coiled by double stranded DNA.
  6. Core or nucleosome made up of histone protein is known as Nu body.
3. Two nucleosomes are joined by linker DNA.
Stain of chromatin/ chromosome is Feulgen stain = Basic fuschin
1. Feulgen stain exactly reacts with "Deoxyribose".
Euchromatin

Heterochromatin
Light stain
Decondensed DNA
Active gene
Early replicated in S-phase
Dark stain
Condensed form
Inactive gene
Late replicated in S-phase

Chromosome

No. of Chromosome
1. Smallest no of chromosome in
  Haplopappus gracillis.
  
  Largest no of chromosome in
  Ophiglossum (Pteridophyta)
Condensed form of chromatin is called Chromosome.
A chromomere, also known as an idiomere, is one of the serially aligned beads or granules of a eukaryotic chromosome, resulting from local coiling of a continuous DNA thread. Chromeres are regions of chromatin that have been compacted through localized contraction.
1. Meiotic chromosome having beaded structure is known as Chromomere.
Haploid set of chromosome is called genome.
Chromosome is the physical basis of inheritance.
Note: DNA is the chemical basis of inheritance.
1. Chromosomes are filamentous structure which carry hereditary units (genes) and hence called vehicle/ bearer of genes.
Chromosome theory of inheritance was proposed by Sutton and Boveri respectively.
Morphological feature of chromosome of a species is called Karyotype.
1. Diagrammatic representation of karyotype in descending sequence is called Idiogram.
Differential staining of the chromosome due to differential thickening is called Heteropycnosis.
Saliva test in olympic games is related to X-chromosomes (Barr bodies).

Ultrastructure of an Eukaryotic chromosome

Pellicle: It is sheath or covering of chromosome.
Matrix: Ground substance
Chromonemata: Coiled threads which form the bulk of chromosomes.

Primary (1o) constriction/ Centromere:

Narrow non stainable area where 2 chromatids are attached.
It provides site for spindle attachment. This site (point) is known as Kinetochore.
The main difference between centromere and kinetochore is that the centromere is a DNA region whereas kinetochore is an assembling protein complex in the centromere.

The centrosome is an organelle that serves as the organizing centre of all microtubules in an animal cell

Types of Chromosome on the basis of position of centromere

Acentric chromosome	Metacentric chromosome	Submetacentric chromosome	Acrocentric chromosome	Telocentric chromosome	Holocentric/ Polycentric/ Diffused centric chromosome
Chromosome without centromere	Centromere in middle i.e., at the centre Arms are of equal size. Anaphasic stage 'V' shaped	Centromere submedian i.e., near to centre. Anaphasic stage. 'L' shaped.	Centromere subterminal i.e., near to top. Anaphasic stage. 'J' shaped.	Centromere terminal; Anaphasic stage. Only one arm or chromosome with single arm. 'I' shaped or rod like.	Whole surface functions as centromere E.g: Lujula

Shape of chromosome is best studies in Anaphase.
Structure, morphology, size, number, etc. can be best studied in Late Prophase and Metaphase (More appropriate metaphase).
The ratio of length of the two arms of chromosomes is called centromeric index.

Secondary (2o) constriction-I:
1. Also known as NOR (Nuclear Organiser Region)
2. Biogenesis (formation) of Nucleolus is at 2o constriction-I of SAT chromosome in telophase.
3. Contains genes for transcription of r-RNA.
Secondary (2o) constriction-II:
1. It contains genes for transcription of t-RNA.
Satellite/ Trabant:
1. Knob like structure near to 2o constriction-I is called satellite.
2. The chromosome bearing satellite is called SAT chromosome.
  1. When SAT chromosome contain secondary satellite then it is called Tandem SAT.
3. There are at least 2 SAT chromosomes per diploid nucleus.
Telomere:
1. It is terminal end/seal end of chromosome.

Notes
1. Skeletons of Cell
  1. Exoskeleton = Cell wall
  2. Endoskeleton = Endoplasmic reticulum
  3. Cytoskeleton = Microtubules, Microfilaments and Intermediate filaments
2. Sizes
  1. Largest
    1. Largest cell component = Nucleus
    2. Larges cell organelle (In plant) = Chloroplast
    3. Largest cell organelle in animal = Mitochondria
    4. 2nd largest cell organelle in plant = Mitochondria
  2. Smallest
    1. Smallest cell organelle = Ribosome
3. Semi-autonomous organelles
  1. Contains
    1. DNA,
      1. DNA is simple, circular, double stranded.
    2. RNA,
      1. Ribosomes are 70s type.
    3. ribosomes.
  2. Replicate independent of Nuclear DNA.
  3. Plastids
    1. Plastids carrying genetic information is called Plastidome.
  4. Mitochondria
    1. These are called Endosymbionts of cell or Prokaryotic cell within eukaryotic cell or cell within cell.
    2. Biogenesis: Mitochondria divide by binary fission to form new ones due to DNA.
    3. Apoptosis is programmed cell death ☠ caused by DNA of Mitochondria.

Euchromatin	Heterochromatin
Light stain Decondensed DNA Active gene Early replicated in S-phase	Dark stain Condensed form Inactive gene Late replicated in S-phase

Smallest no of chromosome in Haplopappus gracillis.	Largest no of chromosome in Ophiglossum (Pteridophyta)